Field of the Invention
The present invention relates to a tool life estimating device.
Description of the Related Art
Typically, a cutting edge of a tool used on a machine tool wears with the passage of time as it is used in machining, causing increase in cutting resistance. Also, as the wear progresses, the machining accuracy of the tool deteriorates, making it difficult to maintain prescribed machining accuracy required for a workpiece. The tool thus reaches the end of its life. The tool that has reached the end of its life needs to be replaced by another one, otherwise it would not be able to continue the machining. However, when the tool reaches the end of its life during automatic operation of the machine tool, it may happen that the tool cannot be replaced immediately in the absence of an operator at the site when the end of the life of the tool is reached, which is one of the factors that hinder the efficiency of the machining cycle. For that reason, a technique for estimating the tool life in advance is of importance.
It is difficult to estimate the life of a tool on or in a machine tool because it varies depending on the workpiece to be machined and the machining conditions. Although it is possible to use a method for estimating the tool life according to the machining time and the number of times of the machining, the accuracy of the estimation by this method is not high and in some cases the operator has to check the tool each time to determine the tool life.
As a conventional technique relating to tool life estimation, Taylor's lifetime equation is known (Japanese Patent Laid-Open No. 11-170102, etc.). When estimating the tool life using the Taylor's lifetime equation, it is possible to estimate the tool life under the various machining conditions by defining a constant based on the machining conditions such as the tool to be used in the machining and the material of the workpiece, and by applying the constant that has been defined to the Taylor's lifetime equation. In addition, a technique for estimating a life of a tool based on machining time, the number of times of machining, and the like has also been proposed (Japanese Patent Laid-Open No. 2002-224925, etc.).
However, when the life of the tool is to be predicted using the Taylor's lifetime equation, the drawback is that the constant of the equation needs to be calculated according to the machining conditions, as a result of which determination of the constant for a machine tool whose machining conditions frequently change becomes complicated, making it difficult to apply the constant to the equation.
Also, when estimating the life of the tool based on the machining time, the number of times of machining, and the like, it is necessary to record the machining times and the numbers of times of the machining for respective tools. In addition, since the estimation method for estimating the tool life depends upon on rules of thumb based on actual machining, a problem arises that prediction of the tool life is difficult in a situation where the machining conditions frequently change.